1. Field of the Invention
The present invention relates to a router, a terminal apparatus, a communication system, and a routing method.
2. Description of the Related Art
Conventionally, a router 202 shown in FIG. 1 is used as a router that performs transferring of a real time data packet transmitted from a transmission terminal. To begin with, the transmission terminal transmits a route setup packet necessary for setting up a route to transfer the data packet. A divider 221 receives the route setup packet and inputs it to a header processing unit 222. The header processing unit 222 records in a flow label table 223 source address of the transmission terminal, a flow label and a port address of the next router based on the information included in the route setup packet. Thereafter, the header processing unit 222 inputs the route setup packet to a routing unit 225. The routing unit 225 transfers the route setup packet to the next downstream router. In this manner, the router 202 sets up the route for transferring the data packet.
Next, the transmission terminal transmits the data packet. The divider 221 receives the data packet, and divides it into a header and a payload. The divider 221 inputs the header to the header processing unit 222. The header processing unit 222 obtains the flow label from the header. Using the obtained flow label, the header processing unit 222 then searches the flow label table 223 and obtains the address for the transfer destination router of the data packet.
Furthermore, the divider 221 inputs the divided header and payload into a restructuring unit 224. The restructuring unit 224 creates a data packet by restructuring the inputted header and payload, and inputs it to the routing unit 225. The header processing unit 222 controls the routing unit 225 so as to transfer the data packet to the address of the obtained transfer destination router. The routing unit 225 transfers to the next router the data packet, which has been obtained from the restructuring unit 224, under the control of the header processing unit 222.
With this type of router 202, the flow label is recorded in the router 202. Accordingly, there is an advantage of allowing the router 202 to achieve speedy routing of the data packet along a set route by using the flow label.
However, with the conventional router 202, a data packet to be transferred along the set route is transferred in all cases. Accordingly, the router 202 along the set route even transfers to the reception terminal a data packet that has arrived late at the router 202 with a delay time that has exceeded the acceptable delay time of the application. In other words, even in a case where a delay in the transfer of the data packet in the network occurs, and the data packet no longer satisfies the application quality since it has not been able to reach the reception terminal within the acceptable delay time, the router 202 will still transfer that data packet to the reception terminal.
If the reception terminal receives that kind of data packet, it will simply discard the data packet since it cannot be normally recreated as an application. In this manner, there are cases where the conventional router 202 transfers to the reception terminal a data packet that is useless thereto. In other words, there are cases where the conventional router 202 carries out unnecessary transfer processing. Furthermore, there are cases where network resources along the route are wasted due to the router 202 performing such unnecessary transfer processing.